Page 68 - Journal of Special Operations Medicine - Fall 2016

Figure 3 Schistosomiasis screening tests. increased for all species. The combination of Bilharzi-
20
ose Fumouze indirect hemagglutination assay (Fumouze
Diagnostics, Levallois-Perret, France) and Schistosoma
mansoni IgG-ELISA (ELISA/NovaTec; NovaTec Immun-
diagnostica, Dietzenbach, Germany) yielded an overall
sensitivity of 89.2% and specificity of 98.1%. Both of
20
these tests are commercially available. Despite promis-
20
ing results, there are drawbacks to serologic studies for
Schistosoma. Antibody production typically lags expo-
sure by 4 to 7 weeks but can lag as much as 6 months
for some individuals. A further drawback is that these
20
tests cannot differentiate between a recent infection and
a previous infection. This can make results difficult to
20
Laboratory interpret in patients who deploy multiple times to en-
The textbook diagnosis of schistosomiasis would re- demic areas.
veal an elevated eosinophil count with ova detected in
the feces or urine; however, these laboratory studies are Treatment
unreliable in travelers. 4,5,11,13 In retrospective studies of
travelers, eosinophilia was noted in 36% to 73% of pa- The CDC recommends treatment of schistosomiasis
tients with schistosomiasis. 5,11,13 This means that 27% to with praziquantel. Treatment should begin 6 to 8 weeks
64% of schistosomiasis-positive patients had normal eo- following exposure, which will allow the parasites to
sinophil counts, which is a very broad range. The high- mature to the adult form, the only form susceptible to
est incidence of eosinophilia was in patients with acute the drug. 12,21 Evidence suggests that administration of
schistosomiasis. In a prospective study of 1,200 trav- praziquantel before this time-frame leads to treatment
13
elers, eosinophilia was found to have a positive predic- failure and greater incidence of advancement of the dis-
tive value of 0% and a negative predictive value of 99% ease to its chronic form. 15,21
for an infection with four separate helminthes, including
schistosomiasis. However, those numbers are likely to be There are many studies confirming the efficacy of pra-
4
skewed due to the low prevalence of schistosomiasis in ziquantel in treating shistosomiasis in endemic popula-
the study. Detection of ova has an even less impressive tions. 12,22 A cure rate for S. mansoni between 60% and
13
yield for infected travelers, with only 8.8% to 26.9% of 95% is attained after the administration of one dose of
patients having ova in stool or feces. 5,11,13 These labora- 40mg/kg praziquantel 6,12 and increases to 95% to 100%
tory tests have proved to be useful in endemic popula- when this treatment is repeated 6 weeks later. Com-
12
tions, who usually have a large parasite burden but do bination therapy with artemisinin derivatives, such as
not have the same efficacy in travelers. On the other mefloquine, has shown promise in reducing worm bur-
hand, serologic studies have proved to be an effective den and increasing the effectiveness of praziquantel in
means to detect schistosomiasis infection in this group. eradicating the infection. 23

Serological detection of schistosomal antibodies has While these data are reassuring for endemic popula-
been used in travelers for more than two decades with tions, they do not necessarily correlate into potential
success. This test is a simple blood draw that can be cure rates in military personnel. There are few studies
13
sent to a commercial laboratory. Serologic tests will confirming the efficacy of praziquantel in the treatment
yield three types of results: positive, negative, or indeter- of shistosomiasis in nonendemic populations. Reports
23
minate. The CDC reports excellent results for detection on European travelers suggest higher failure rates with
of S. mansoni (sensitivity 99%, specificity 99%) and S. praziquantel. Helleberg and Thybo looked at travelers
24
heamatobium (sensitivity 95%, specificity 99%). A 3 months after treatment with one dose of 40–60mg/
19
study in 2012 evaluated the sensitivity and specificity kg praziquantel and found ova in 20%. Considering
of eight serological assays in travelers. The study found the previous discussion on the sensitivity of parasitol-
sensitivities that ranged from 41% to 78% and specifici- ogy, this is an alarmingly high rate. Another patient in
ties that range from 76% to 100%, with the best test the same study demonstrated increased IgE and anti-
achieving 75.7% and 98.1%, respectively. The high body titers 2 years after therapy. Further, 13% of these
20
24
specificity was in part because the study scored indeter- patients had findings concerning for persistent infection
minate results as positive. All eight assays were more despite negative, from Italy, studies. 24
20
sensitive for S. mansoni than for S. haematobium. The
20
study also found that by reviewing the results of two Another report from Italy followed the serology of four
tests simultaneously, sensitivity could be significantly travelers with shistosomiasis after treatment. All of

50 Journal of Special Operations Medicine Volume 15, Edition 3/Fall 2016